Composition, for use in paint, based on a mixture of emulsion(s) and of dispersion(s) of polyol polymer and coating(s) produced therefrom

ABSTRACT

The subject of the present invention is a composition comprising: 
     at least one masked or unmasked polyisocyanate in the form of an aqueous emulsion whose mean size is between 0.1 and 10 micrometres and preferably smaller than 2 and larger than 0.2 micrometres, 
     at least one polyhydroxylated polymer, advantageously a polyol, in the form of a second aqueous dispersion whose mean size is between 10 and 200 nanometres. 
     This composition is defined in that the quantity of polyol in the mixture is chosen so as to meet one of the following two constraints: 
     the polyol content, expressed in mass percent, is at least equal to 35-0.75R, advantageously at least equal to 40-0.75R, preferably to 45-0.75R; 
     the polyol content, expressed in mass percent, does not exceed 45-2R, advantageously does not exceed 40-2R, preferably 35-2R 
     with R equal to the ratio of the mean size (d 50 ) of the emulsion to that of the polyol dispersion. 
     Application to organic synthesis.

This application is a divisional of U.S. application Ser. No.09/600,355, filed on Feb. 12, 1996, now U.S. Pat. No. 5,739,206.

The present invention relates to mixtures of emulsions with dispersionsof polymer. It relates more particularly to the stability of a polyoldispersion conjointly with an emulsion of isocyanate which is in mostcases masked.

Such compositions are especially useful for varnishes and paint, butthey can be useful for any application employing the condensationproperties of isocyanates. They can also be useful in any field in whichemulsions of isocyanates, in most cases blocked ones, need to coexistwith dispersions of insoluble alcohols of different particle size andespecially in formulations for agriculture.

In the remainder of the present description the term dispersion will beemployed for polymers containing hydroxyl functional groups andespecially polyols, while the expression emulsions will be employed forisocyanates, whether blocked or not.

The use of organic solvents is increasingly frequently criticized by theauthorities responsible for safety at work because these solvents, or atleast some of them, are reputed to be toxic or chronically toxic. Thisis why attempts are being made to develop more and more techniques whichreplace techniques in a solvent medium in order to overcome thedisadvantages associated with the solvents.

One of the most frequently employed solutions lies in the use ofemulsions or dispersions in water.

To produce paint or varnish films, two dispersions are mixed, anemulsion containing the isocyanate, which may be blocked, and adispersion of polyol.

The mixture of the dispersions, which may also contain pigments andfillers, is then deposited on a substrate in the form of a film with theaid of conventional techniques for applying industrial paints. When thepreparation contains blocked isocyanates the combination of film plussubstrate is cured at a sufficient temperature to ensure the deblockingof the isocyanate functional groups and the condensation of the latterwith the hydroxyl groups of the polyol particles.

In the present description the particle size characteristics frequentlyrefer to notations of the d_(n) type, where n is a number from 1 to 99;this notation is well known in many technical fields but is a littlerarer in chemistry, and therefore it may be useful to give a reminder ofits meaning. This notation represents the particle size such that n %(by weight, or more precisely on a mass basis, since weight is not aquantity of matter but a force) of the particles are smaller than orequal to the said size.

In the remainder of the description the polydispersity index will beemployed, which is defined as

    I=(d.sub.90 -d.sub.10)/d.sub.50

Typically the ratios of the mean sizes (d₅₀) between the isocyanateemulsion and the polyol dispersion are between 2 and 200. Thus, the meansizes of the isocyanate emulsions manufactured according to thetechnique described in the French Patent Application filed on 31.3.1993under No. 93 03795 and published under No. 2703358 on 7.10.94 have meansizes of between 0.1 and 10 micrometres and more generally between 0.3and 2 micrometres. The polyol dispersions employed in combination withthese emulsions have mean sizes measured by quasielastic scattering oflight which are between 20 and 200 nanometres and more generally between50 and 150 nanometres.

When dispersions of different sizes are mixed, which is generally thecase, so as to obtain molar ratios between the NCO and OH groups ofbetween 0.3 to 10 and more preferably between 0.8 and 1.5, aninstability is observed in the mixtures of the two dispersions.

To give an example, this instability is reflected in a fast macroscopicseparation, generally over a few minutes, to give, on the one hand, afluid phase and, on the other hand, a very viscous phase.

This results not only in it being impossible to preserve (store) thesemixtures, but also in extreme difficulty in applying this mixture to thesurface which it is desired to cover according to the usual techniquesfor the application of paints and varnishes. If these unstable mixturesare applied onto a substrate, such as onto a sheet of glass or metal,the resulting film is not transparent but looks opaque and heterogeneousand is therefore not suitable.

These problems are particularly acute in the case of isocyanates,whether masked or not, when the latter are mixed with insoluble polyolsdispersed in water.

Thus, one of the objectives of the present invention is to provide atechnique which makes it possible to provide fluid and stable mixturesof an isocyanate emulsion with dispersions of polyols which are stableper se, especially without there being any need to add any additional orneutralizing additive, for example to adjust a pH.

Another objective of the present invention is to provide compositionscomprising an emulsion of masked isocyanates and a dispersion of polyolswhich are physically stable for at least a month.

The other objective of the invention is to is obtain, from these stableand fluid mixtures of this emulsion with a polyol dispersion, filmsexhibiting good gloss, transparency and solvent resistance properties.

These objectives are attained by means of a composition comprising:

at least one masked or unmasked polyisocyanate in the form of an aqueousemulsion whose mean size is between 0.1 and 10 micrometres andpreferably smaller than 2 and larger than 0.2 micrometres,

at least one polyhydroxylated polymer, advantageously a polyol, in theform of an aqueous dispersion whose mean size is between 10 and 200nanometres.

The ratio (R) between the mean sizes of the elementary particles (d₅₀)of the emulsion and that of the polyol dispersion being at least equalto 2 is more frequently between 8 and 40 and more generally around 30.

It is highly desirable that the emulsion and/or the dispersion should bedispersed as little as possible.

Thus, in the case of the polyhydroxylated polymers, the polydispersityindex (defined as I=(d₉₀ -d₁₀)/d₅₀) is at most equal to 2 advantageouslyequal to 1, the best results being obtained with values of 0.2 to 0.1 oreven less.

Thus in the case of the polyisocyanates, masked or otherwise, thepolydispersity index defined as (d₉₀ -d₁₀)/d₅₀ is at most equal to 2advantageously equal to 1. The best results are obtained with values of0.9 to 0.8 or even less.

The formulation regions depend on the ratio R of the mean sizes (d₅₀)between the isocyanate emulsion and those of the dispersion ofpolyhydroxylated polymer(s), advantageously of polyols.

R is equal to the mean size of the emulsion over the mean size of thedispersion of polyhydroxylated polymer, advantageously of polyol.

According to the invention, the quantity of polyhydroxylated polymer,advantageously of polyol, in the mixture is chosen so as to meet one ofthe following two constraints:

the content of polyhydroxylated polymer, advantageously of polyol,expressed in mass percent, is at least equal to 35-0.75R, advantageouslyat least equal to 40-0.75R, preferably to 45-0.75R;

the content of polyhydroxylated polymer, advantageously of polyol,expressed in mass percent, does not exceed 45-2R, advantageously doesnot exceed 40-2R, preferably 35-2R

with R equal to the ratio of the mean size (d₅₀) of the emulsion to thatof the dispersion of polyhydroxylated polymer, advantageously of polyol.

In other words R=(d₅₀ of the emulsion)/(d₅₀ of the dispersion).

Thus, when R is between 2 and 10, this is the constraint according towhich the polyol content expressed in mass percent is at least equal to35-0.75R, advantageously at least equal to 40-0.75R, preferably to45-0.75R, which gives the most significant region of existence.

With R between 10 and 15 it is possible to find viable solutions in oneor other field as defined by the above inequalities.

With R greater than 15, solutions to the problems posed can hardly befound, except in the field defined by the condition according to whichthe polyol content expressed in mass percent does not exceed 45-2R,advantageously does not exceed 40-2R, preferably 35-2R.

Thus in the field where R is between 10 and 15, two stable regions ofexistence coexist.

The ratio of the number of hydroxyl functional groups to the number ofisocyanate functional groups, masked or otherwise, can vary very widely,as shown above.

Ratios which are lower than the stoichiometry promote plasticity, whileratios which are higher than the stoichiometry produce coatings of greathardness. It is rare to have ratios which depart from the rangeextending from 0.5 to 2.

However, in the majority of cases and for the most common applications,to obtain varnish or paint films which are satisfactory, it ispreferable that the quantity, expressed in equivalents, of reactiveblocked isocyanates should be substantially equal to that of the freeand reactive alcohol functional groups, expressed in equivalents, thatis to say corresponding to the stoichiometry. By way of guidance, it maybe indicated that a tolerance of plus or minus 20% relative to the isstoichiometry exists, but it is preferably to employ only a tolerance ofplus or minus 10 or 20%.

The isocyanate emulsions are advantageously made according to thetechnique described in the French Patent Application published under No.2703358 on 7.10.94, filed on 31.3.1993 under No. 93 03795 and entitled:"Process for the preparation of aqueous emulsions of advantageouslymasked (poly)isocyanate oils and/or gums and/or resins and emulsionsobtained".

With regard to the additional components of a composition according tothe present invention, it is possible that it additionally comprises atleast one catalyst for releasing the masked isocyanates, and especiallytin-based catalysts which are latent or otherwise. It may be stated thatthese catalysts may be present either within the polyol phase or withinthe masked isocyanate phase or in dispersed form within the continuousaqueous phase. Finally, they may be dissolved in the aqueous phase.

The polyol dispersions which can be used for the invention areconventional products employed in the paint and varnish industry. Inmost cases they are (co)polymers manufactured in emulsion according tothe conventional processes of radical or bulk polymerization.

The following commercial polyester or acrylic resins may be mentioned byway of examples, or rather as paradigms, the list not being restrictive:

Rhoplex® AC-1024 (compare the datasheet published in 1984);

Joncryl® 8300 (compare the datasheet CJ8300e/B2);

Sancure® Water Borne Urethane 815 (compare the datasheet revised on Jan.2, 1992 and printed on Apr. 1,1994);

Synthacryl® VWS 1505 (compare the datasheet published in September1991).

These products are in the form of aqueous dispersions (or emulsion) withsolids contents of between 20 and 60%. The polyols are characterized bytheir hydroxyl group contents which are either given by the manufactureror are determined by analysis.

A pigment known per se may be added in the case of paints, provided thatit is inert towards the constituents of the composition.

Although it is possible according to the present invention to employunmasked isocyanates, and as the latter are not very stable in water,the preferred isocyanates are those which are masked, especially bymasking agents which are themselves known, such as phenols, ketoneoximes and especially methyl ethyl ketone oxime and various pyrazoles.

The preferred isocyanates are those in which the nitrogen of at leastone of the isocyanate groups is attached to a carbon with sp³hybridization advantageously carrying one, and preferably two, hydrogenatom(s). The isocyanates in which all the functional groups have thischaracteristic (possibly with its preferred options) are highly valued.

It is possible in particular to mention isocyanates, masked orotherwise, which have one or more isocyanuric rings and/or at least oneof the functionalities of biuret or dimer type.

It is preferable that the isocyanates should exhibit the abovementionedtwo characteristics, namely oligomerism and aliphatic character on atleast one of the isocyanate functional groups.

The water content of the said compositions is advantageously at leastequal to one third of the mass of the composition, advantageously atleast 2/5.

The preferred polyols are in the form of an aqueous dispersion; theyhave a mean size smaller than 200 nanometres, which offers a greaterscope for formulation in combination with the isocyanate emulsions.Preference is given to aqueous dispersions with a low content ofwater-soluble compounds such as alcohols and amines, which can result inthe coagulation of the isocyanate emulsion. It is therefore highlydesirable that the cumulative content of various alcohols and aminesshould be lower than those that produce a coagulation of the isocyanateemulsion.

The present invention is also aimed at the coatings obtained from thecompositions in accordance with the present invention. These coatingsmay be obtained by crosslinking, in particular by curing at atemperature close to that corresponding to the release of the maskedisocyanates, optionally in the presence of one or more catalysts.

The following nonlimiting examples illustrate the invention.

EXAMPLE 1

Tolonate D2® is a mixture of oligomers containing an isocyanuric ringessentially of the trimer masked with methyl ethyl ketone oxime.

Joncryl® 8300 is an acrylic dispersion of mean diameter 75 nm, measuredby quasielastic light scattering. The isocyanate is an emulsion ofTolonate® D2 of mean diameter equal to 1.14 μm measured with the aid ofa Sympatec® particle size analyser. The ratio of the sizes R is equal to15.2. The mixture containing 36.4% by weight of Joncryl® and 10.7% byweight of Tolonate®, which corresponds to an NCO!/ OH! molar ratio of1.05, is fluid and stable. 100-μm films are spread on glass sheets withthe aid of an automatic Touzard et Matignon applicator reference ASTM823, method D. After curing for 20 minutes at 150° C. a 30-μmtransparent film is obtained. The Persoz hardness of the film is 208.The gloss, measured on an Ericksen contrast card at an angle of 20° is61.4 and 87.2 at an angle of 60°. In addition, the film obtainedexhibits good resistance to methyl ethyl ketone solvents and to acetone.

The 6%/1.9% Joncryl®/Tolonate® mixture, which corresponds to an NCO/OHratio of 1.05, gives rise to a macroscopic phase separation and the filmobtained is heterogeneous and cloudy.

EXAMPLE 2

Synthacryl® VSW 1505 is a polyol dispersion of mean diameter 65 nmmeasured by quasielastic light scattering. The isocyanate is the same asthat employed previously. The ratio of the sizes R is equal to 17.5. Themixture containing 28.6% by weight of Synthacryl® VSW 1505 and 19.9% byweight of Tolonate®, which corresponds to an NCO!/ OH! molar ratio of2.62, is fluid and stable. 100-μm films are spread onto glass sheetswith the aid of an automatic Touzard et Matignon applicator referenceASTM 823, method D. After curing for 20 minutes at 150° C. a film isobtained which exhibits good resistance to methyl ethyl ketone solventsand to acetone.

The 15%/10% Synthacryl® VSW 1505/Tolonate® mixture, which corresponds toan NCO/OH ratio of 2.52, gives rise to a macroscopic phase separationbetween a fluid phase and a flocculated mixture.

EXAMPLE 3

Rhoplex® AC 1024 is a polyol dispersion of mean diameter 135 nm ,measured by quasielastic light scattering. The isocyanate is the same asthat employed previously. The ratio of the sizes R is equal to 8.4. Themixture containing 15% by weight of Rhoplex® AC 1024 and 10% by weightof Tolonate®, which corresponds to an NCO!/ OH! molar ratio of 4.8, isfluid and stable. 10 100-μm films are spread onto glass sheets with theaid of an automatic Touzard et Matignon applicator reference ASTM 823,method D. After curing for 20 minutes at 150° C. a film is obtainedwhich exhibits good resistance to methyl ethyl ketone solvents and toacetone.

The 40%/10% Rhoplex® AC 1024/Tolonate® mixture corresponds to an NCO/OHratio of 1.8. This mixture gives rise to a macroscopic phase separationbetween a fluid phase and a flocculated mixture.

EXAMPLE 4

Sancure 815 is a polyol dispersion of 35 nm mean diameter measured byquasielastic light scattering. The isocyanate is the same as thatemployed previously. The ratio of the sizes R is equal to 32.5. Themixture containing 20% by weight of Sancure and 10% by weight ofTolonate® is fluid and stable.

The corresponding 8%/8% Sancure/Tolonate® mixture gives rise to amacroscopic phase separation between a fluid phase and a flocculatedmixture.

What is claimed is:
 1. A process of coating a surface comprising thesteps of:(1) coating said surface with a composition physically stableone month or more upon storage, consisting essentially of:at least onemasked polyisocyanate in the form of an aqueous emulsion whose mean sizeis between about 0.1 and about 10 micrometers; and at least onepolyhydroxylated polymer in the form of an aqueous dispersion whose meansize is between about 10 and about 200 nanometers, wherein the quantityof polyhydroxylated polymer(s) in the mixture in mass percent is atleast equal to 35-0.75R or does not exceed 45-2R, R being equal to theratio of the mean size (d₅₀) of the emulsion to that of the dispersionof polyhydroxylated polymer; and (2) crosslinking said composition.
 2. Aprocess according to claim 1, wherein the mean size of the aqueousemulsion is smaller than about 2 and larger than about 0.2 micrometers.3. A process according to claim 1, wherein the polyhydroxylatedpolymer(s) is a polyol.
 4. A process according to claim 1, wherein thequantity of polyhydroxylated polymer(s) in the mixture is at least equalto about 40-0.75R or does not exceed about 40-2R.
 5. A process accordingto claim 4, wherein the quantity of polyhydroxylated polymer(s) in themixture is at least equal to about 45-0.75R or does not exceed about35-2R.
 6. A process according to claim 1, wherein said maskedpolyisocyanate(s) has(have) a polydispersity index defined as (d₉₀-d₁₀)/d₅₀ not exceeding
 2. 7. A process according to claim 6, whereinsaid masked polyisocyanate(s) has(have) a polydispersity index definedas (d₉₀ -d₁₀)/d₅₀ equal to
 1. 8. A process according to claims 1,further comprising at least one catalyst of release of the maskedisocyanates.
 9. A process according to claims 8, wherein said catalystof release of the masked isocyanates is a tin-based catalyst or a latenttin-based catalyst.
 10. A process according to claims 1, wherein thewater content of the said composition is at least equal to about onethird of the mass of the composition.
 11. A process according to claims10, wherein the water content of the said composition is at least about2/5.
 12. A process according to claim 1, wherein said polyisocyanatehas(have) one or more isocyanuric rings.
 13. A process according toclaim 1, wherein said polyisocyanate has(have) one or more biuretfunctionality.
 14. A process according to claim 1, wherein saidpolyisocyanate is chosen from those in which the nitrogen of at leastone of the isocyanate functional groups, is attached to a carbon withsp³ hybridization carrying one or two hydrogen atom(s).
 15. A processaccording to claim 1, wherein said polyisocyanate is masked by a maskingagent selected from the group consisting of phenols, ketone oximes andpyrazoles.
 16. A process according to claim 15, wherein the maskingagent is methyl ethyl ketone oxime.
 17. A process according to claim 3,wherein the polyol is a nanolatex.